Medieval sacred Latin monody (MSLM), which is also known as Gregorian chant, has justly been claimed to be the foundation of Western professional musical culture. Indeed, classical Western musical notation as we know it today, originates from the earliest attempts to write down MSLM in the 10th century. Through this MSLM appears to be one of the main identifiers of our professional musical culture and therefore deserves multifaceted scholarly attention. This project is mainly conducted in the realm of cognitive musicology and uses the tools and know-how of psychology of music and musical acoustics. The main goal of the project is to obtain new knowledge about MSLM through analysing its performance. This project is a four-step perception experiment: (1) five solo performers who are mainly specialised in performing MSLM will record a piece from MSLM using the original notation from a selected 10th century manuscript; (2) based on the digital measuring of the recording, an accurate transcription in classical Western musical notation will be created; (3) a professional singer, competent in reading complicated notation and not acquainted with performance of MSLM, will then learn and record the piece, using the transcription; (4) two recordings will be compared on an aesthetical basis using test persons and through a comparison of digitally measured temporal structures of the two recordings. Performance of MSLM is known by its unusual sound-scape, which clearly differentiates from performance of other vocal repertoires. With this project I intend to find out whether this unusualness originates from the repertoire and its notational style or rather from the performer and his/her vocal peculiarity and/or spiritual identity. Would the performance using the original notation differentiate from the performance using the transcription? Answering to this question might reveal new facets of MSLM and through this give important new knowledge about the roots of our musical culture.